1. Field of the Invention
The present invention relates to an apparatus for supporting and guiding a round bar at the downstream side of the mold while the round bar is cast by the continuous rounds casting machine.
2. Description of the Prior Art
A conventional type of supporting and guiding apparatus for continuous rounds casting, as shown in FIG. 1 depicting the cross section thereof, is in such a structure that pillar-like frames 1, 1, . . . are arranged in positions surrounding the round bar A so that the longitudinal direction thereof is along the drawing direction of the round bar A and rotational axes of four rolls 2, 2, . . . are fixed to four pillar-like frames respectively so that the four rolls 2, 2, . . . may be brought into rolling-contact with the round bar A at four points on the periphery thereof. A plurality of sets of rolls each consisting of four rolls 2, 2, . . . as above-mentioned are provided along the longitudinal direction of pillar-like frames 1, 1, . . .
In such a conventional structure as above, when the size (diameter) of a round bar A is changed due to the replacement of molds, a supporting and guiding apparatus for continuous rounds casting must also be replaced by the other fit one to the changed size, thereby requiring preparation of various kinds of supporting and guiding apparatus. For example, on the assumption that the kinds of sizes of round bars castable by the continuous casting machine are five and the number of strands is six, at least thirty sets of apparatus are required. In practical operation, however, two to three times as many sets as those required at the minimum, that is, 60 to 90 sets, are required for troubles and repairs of apparatus. This large number of sets requires a large expense for maintenance and management of the apparatus and a large space for storage thereof.
Further, there is a problem since a long period of time for the replacement of apparatus is required. As an index of productivity in continuous casting operation, a monthly casting time rate such as
(Net casting hour/Total hour per month).times.100 (%) is employed. The higher the rate, the greater the productivity. In the continuous casting machine for casting various sizes of round billet, which require the changing of the mold according to the size, it is usual that about five to six hours are required for changing of round bar size because of the replacement of supporting and guiding apparatus along with that of molds. This changing has been a cause of low level of the abovesaid monthly casting time rate.
Further problem is that spaces for setting sprays for cooling the round bar are insufficient since rolls are mounted on four pillar-like frames disposed around a round bar. Accordingly, almost no gaps are provided between the frames, rolls, and round bar for setting the sprays.
Moreover, a dummy bar used in the beginning of continuous casting is attended by a problem as follows:
A dummy bar is roughly divided into three parts, one being a head to prevent the molten metal from flowing out from the mold at the start of molten metal pouring and to serve as a connecting part with a round bar to be cast and the other being a common part and a transition part for drawing the head in the direction of drawing of the bar. In the conventional apparatus, the transition part must have a diameter which is the same as diameter of the billet and is sufficiently as long to reach the lowermost end of the supporting and guiding apparatus because rolls are fixed so as to surround a round bar from four directions.